The art establishment needs to make its support for Ai Weiwei visible

A curator's signature on an online petition is not enough. The great museums should publicise China's detainee via their sites

Chinese artist Ai Weiwei with his installation 'Sunflower Seeds' inside the Turbine Hall at Tate Modern gallery in London, October 2010; in April 2011, Ai was arrested and detained by the Chinese authorities. Photograph: Lennart Preiss/AP

One of the most successful attempts to galvanise public support for the detained Chinese artist Ai Weiwei has been a petition started by the Guggenheim Museum and other art institutions. To date, it has been signed by over 140,000 individuals and organisations. The petition has been so popular, in fact, that the social action website Change.org, which hosts it, said its site has been the target of repeated cyber-attacks originating in China and which, the organisation believes, are aimed directly at taking down the Ai Weiwei petition. The attacks have been so disruptive to Change.org that they've called on the FBI for assistance and a US lawmaker, championing their cause, is calling on Secretary of State Hilary Clinton to tell the Chinese government to stop the attacks.

Ai Weiwei and his associates – Wen Tao, his friend and assistant; Zhang Jingsong, his cousin and driver; Hu Mingfen, his accountant; Liu Zhenggang, a designer — were rounded up by Chinese authorities on 3 April, when police arrested Ai as he was about to board a plane in Beijing. Although there has been chatter in Beijing-controlled media about crimes supposedly committed by Ai, no charges have been brought against the man rated the world's top artist.

Despite the popularity of the Change.org petition and the international furore surrounding it, however, if you visit the websites of virtually any of the petition's major signatories, you would not know that Ai was incarcerated. Judging from these websites, all is well with the world.

The Guggenheim is currently promoting an exhibition about Kandinsky at the Bauhaus; the Los Angeles County Museum of Art is talking up an exhibition about Elizabeth Taylor in Iran; and even the Tate Modern in the UK, which until a few weeks ago hosted Ai's Sunflower Seed installation, doesn't disturb its homepage to inform visitors that the artist has been criminally detained, hasn't been charged with any crime, hasn't been heard from for over eight weeks. These three institutions are not alone in their homepage silence. Numerous other headlining signatories of the Change.org petition also have nothing to say on the matter on their homepages, including: MoMA; Art Institute of Chicago; Hammer Museum; Nelson-Atkins Museum of Art; Brooklyn Museum; Institute of Contemporary Art, Boston; Louisiana Museum of Modern Art, Denmark; Montreal Museum of Fine Arts; San Francisco Museum of Modern Art; Queensland Art Gallery, Australia; Harvard Art Museums; Museum of Arts and Design, New York; and The Andy Warhol Foundation for the Visual Arts.

On the other side of the ledger, the US city of Minneapolis deserves credit – as both the Minneapolis Institute of Arts and the Walker Art Centre have had some text on their sites about the Change.org petition, while the Serpentine Gallery in London also has text about the petition and a photo of Ai. For its part, the Stedelijk Museum, Amsterdam, has a photo of Ai Weiwei at the Tate Modern tossing his sunflower seeds heavenward – and a reference to the Change.org petition – as part of a series of images that cycle through in a Flash slideshow.

Finally, a tip of the cap goes to the Taipei Contemporary Art Centre, which has a brave message on its homepage calling on its mainland adversary to release all activists and to protect the creative freedom of artists, a freedom it says is a sign of any country's mature development. That's four institutions out of 20 publicly supporting Ai Weiwei on their websites – and not the biggest names in the art gallery and museum world, by any stretch of the imagination. This is surely a golden opportunity that sadly has been missed. Yet, as Hari Kunzru writes of the Montreal Museum (currently hosting a China show), it's also a golden opportunity that can still be taken.

The Chinese government, having abducted Ai Weiwei, is making a concerted effort to make him invisible, including removing all references to him from public media, including the internet. They can do this in their land. They should not be allowed to do it in any other. Ai Weiwei was committed and creative in his use of the web when he was free to express himself. He would expect no less of us now that his freedom has been taken from him and he is relying on others to fight for his release.